Field of the Invention
The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device that may improve reliability of an organic light emitting diode layer.
Discussion of the Related Art
Organic light emitting display devices are self-emitting devices having low power consumption, a fast response time, high emission efficiency, high luminance, and a wide viewing angle. The organic light emitting display devices are classified into a top emission type and a bottom emission type, based on a transmission direction of light emitted from an organic light emitting device. In the bottom emission type, a circuit element is disposed between an emission layer and an image displaying surface which results in a lower aperture ratio. In the top emission type, the circuit element is not disposed between the emission layer and the image displaying surface which results in a higher aperture ratio.
FIG. 1 is a cross-sectional view illustrating an organic light emitting display device of the related art. The organic light emitting display device includes a thin film transistor layer 11, an organic light emitting diode layer 12, an adhesive layer 13, and an encapsulation layer 14 that may all be formed in an active area AA on a substrate 10.
The thin film transistor layer 11 can include an active layer, a gate insulating film, a gate electrode, an interlayer dielectric, a source electrode, and a drain electrode. The thin film transistor layer 11 transfers a signal required for luminescence of the organic light emitting diode layer 12.
The organic light emitting diode layer 12 can include an anode electrode, an organic light emitting layer, and a cathode electrode. The organic light emitting diode layer 12 displays an image by using light emitted from the organic light emitting layer and passed through the cathode electrode.
The adhesive layer 13 is provided to cover an upper surface and a side of the organic light emitting diode layer 12. The adhesive layer 13 adheres the encapsulation substrate 14 to the organic light emitting diode layer 12.
The encapsulation substrate 14 is provided on the adhesive layer 13 to encapsulate the substrate 10 provided with the organic light emitting diode layer 12. The encapsulation substrate 14 encapsulating the substrate 10 protects elements provided in the substrate 10.
The aforementioned organic light emitting display device according to the related art can have a problem due to a crack in the organic light emitting display device. The encapsulation substrate 14 has a strong anti-water permeation effect in view of its material property, whereas the adhesive layer 13 has a weak anti-water permeation effect. For this reason, particles such as water permeate into an area S of the adhesive layer 13, which is provided at the side of the organic light emitting diode layer 12. A condition of the organic light emitting diode layer 12 can degrade due to the water permeation.
To prevent water from permeating into the area S of the adhesive layer 13, the organic light emitting display device according to the related art includes the adhesive layer 13 that is provided thinly. However, although water permeation through the side of the organic light emitting diode layer 12 can be prevented (i.e., avoided), a problem exists in that a crack in the organic light emitting display device is more likely to occur due to physical damage caused by an external impact. The crack in the organic light emitting display device can result in a dark spot occurring in some areas of the organic light emitting display device.
Next, FIG. 2 illustrates delamination between the organic light emitting layer and the cathode electrode of the organic light emitting display device according to the related art. In particular, a flexible organic light emitting display device according to the related art can have the problem of delamination between the organic light emitting layer and the cathode electrode of the organic light emitting diode layer 12. For a flexible screen, a position of a neutral plane can be controlled to be within a plurality of deposition structures shown in FIG. 1 to distribute an internal force appropriately. The encapsulation substrate 14 of the plurality of deposition structures can be provided to have a relatively great thickness. The neutral plane can be disposed at a boundary area between the adhesive layer 13 and the encapsulation substrate 14.
Due to the encapsulation substrate 14 having a relatively great thickness and the neutral plane being disposed at the boundary area, a problem of an application of an undesirable tensile force can occur. In particular, the problem is that a strong tensile force being applied to the organic light emitting diode layer 12 below the adhesive layer 13 can cause the organic light emitting display panel to be bent to be downwardly convex. The downwardly convex organic light emitting display panel can result in delamination occurring between the organic light emitting layer and the cathode electrode of the organic light emitting diode layer 12. The problem in the organic light emitting display devices according to the related art increases the need of a technique capable of avoiding water permeation through the side of the organic light emitting diode layer 12 and improving stability of the flexible organic light emitting display device.